1. Technical Field
Novel photoresist monomers, polymers thereof, and photoresist compositions using the same are disclosed. In particular, photoresist polymers suitable for a photolithography process using DUV (deep ultraviolet) light sources such as VUV (157 nm) and EUV (13 nm) in fabricating a minute circuit for a high integration semiconductor device, photoresist compositions using the same, and preparation processes therefor are disclosed.
2. Description of the Background Art
In general, a useful photoresist for ArF and VUV has a variety of desired characteristics, such as low light absorbance at the wavelength of 193 nm and 157 nm, excellent etching resistance, and excellent adhesiveness to a wafer. In addition, a photoresist should be easily developable in a commercially readily available developing solution, such as 2.38 wt % and 2.6 wt % aqueous tetramethylammonium hydroxide (TMAH) solution.
Recently, there has been much research done on resins having a high transparency at the wavelength of 193 nm and dry etching resistance similar to novolac resin. However, most of the photoresists are not suitable for VUV due to their poor transmittance at 157 nm wavelength.
Photoresists containing fluorine and silicon have good transmittance at these wavelengths. Unfortunately, most photoresists containing fluorine with a polyethylene or polyacrylate polymer backbone have weak etching resistance, low solubility in an aqueous TMAH solution and poor adhesiveness to the silicon wafer. Furthermore, solubility of the resin is remarkably improved by introducing strong acid alcohol groups (pKa xe2x89xa612), but the resin still remains unsatisfactory as a photoresist. It results from a low glass transition temperature (Tg) of the resin, a low contrast ratio between exposed and unexposed regions, and low adhesiveness to the wafer. On the other hand, photoresists containing silicon require a 2-step etching process of HF treatment and O2 treatment. And it is difficult to remove HF completely, which makes these types of photoresists unsuitable to be applied into production.
In an attempt to overcome the above-described disadvantages, photoresist monomers comprising bisphenol derivatives containing trifluoromethyl and fluorine, and polymers thereof that have low absorbance at the wavelength of 157 nm, and a relatively high glass transition temperature (100xcx9c140xc2x0 C.) are disclosed.
Accordingly, novel photoresist monomers and polymers thereof that can be used for a light source such as ArF (193 nm), VUV (157 nm) and EUV (13 nm) are disclosed.
Photoresist compositions comprising the photoresist polymer described above are also disclosed.
Semiconductor elements produced using the photoresist compositions described above are also disclosed.